An apparatus is known for measuring the induced air mass in internal combustion engines which apparatus includes a bridge circuit connected to a control apparatus, and a temperature-dependent resistor disposed in the induced air flow in one arm of the bridge circuit, the magnitude of the temperature and resistance of the resistor being regulated in accordance with the induced air mass. In such apparatus, the manipulated variable is a standard for the induced air mass. Theoretically, this apparatus produces good measurement results. However, because of the crude operation of the measurement apparatus in motor vehicles, problems occur, particularly after relatively lengthy operation because the surface of the temperature-dependent resistor becomes increasingly dirty.
U.S. Pat. No. 4,196,622, issued Apr. 8, 1980 to Peter, describes an apparatus for increasing the current through the temperature-dependent resistor of this known induced air mass measuring apparatus each time the engine is shut off until such time as the temperature of the temperature-dependent resistor reaches a predetermined temperature sufficient to burn off deposits from the surface of the resistor. However, when the engine is frequently shut off for short intervals of time, the number of burn-off operations performed on the temperature-dependent resistor is much greater than that required to assure good accuracy, and the service life of the resistor may be shortened by such frequent red-hot heating procedures. Also, when the engine is continuously operated for very long periods of time, the number of burn-off operations performed on the temperature-dependent resistor may be much less than that required to assure good measurement accuracy.